Carbon materials having a graphene sheet structure have received attention due to their high elastic modulus and high electrical conductivity. Compounding of such a carbon material having a graphene structure with a synthetic resin makes it possible to reinforce a product made of the synthetic resin or impart electrical conductivity to the product. Particularly, a graphene sheet, a carbon nanotube, exfoliated graphite or the like has a nanoscale size and a large specific surface area. Therefore, such a carbon material is believed to have a high reinforcing effect when compounded with a resin.
In general, it is preferred that the carbon material is uniformly dispersed in the matrix resin to obtain a more effective composite material. Patent Document 1 discloses a method in which a good solvent for a thermoplastic resin and a carbon material is used to achieve a uniform dispersion state. According to this method, a resin composite material having a uniform dispersion state can be obtained as long as a common solvent for the thermoplastic resin and the carbon material exists.